What Is Cardiology? A Guide to the Discipline

Cardiology is the branch of medicine and biomedical science that studies the heart and the blood vessels: how the circulation delivers blood to the body, how that system is regulated, and what happens when it is injured, diseased or malformed. It is both a clinical specialty, diagnosing and treating conditions such as coronary artery disease, heart failure and rhythm disorders, and a research discipline spanning physiology, genetics, epidemiology, imaging, device engineering and large clinical trials. (The name comes from the Greek kardia, heart.) This guide explains what cardiology covers and how its subfields divide up, then adds the research-administration layer that generic overviews leave out: who funds cardiovascular research, how trial endpoints such as MACE are built, how devices and imaging are regulated and used, and typical training paths. It is educational, not medical advice.

What Is Cardiology?

Cardiology is organized around a handful of interlocking questions:

• How does the circulation work? The heart is a muscular pump with four chambers and valves, driven by an electrical conduction system and supplied by its own coronary arteries. Cardiovascular physiology, the study of pressure, flow, contraction and electrical activity, is the basic-science foundation of the specialty.
• What goes wrong? Blocked or narrowed arteries (atherosclerosis and coronary artery disease), heart attack, weakened or stiff heart muscle (cardiomyopathy and heart failure), abnormal rhythms (arrhythmias such as atrial fibrillation), valve disease, congenital defects, and diseases of the aorta and peripheral vessels.
• Who is at risk, and why? Risk factors such as blood pressure, cholesterol, diabetes, smoking and family history, studied through population cohorts and genetics.
• How is it detected and treated? Through electrocardiography, imaging, catheter-based procedures, drugs, implanted devices and surgery, often delivered by a team that includes cardiac surgeons, nurses, imaging specialists and rehabilitation staff.

Cardiology and Cardiovascular Science

Casual usage blurs several terms. Cardiology usually refers to the medical specialty (clinical care plus its research). Cardiovascular medicine is a broader label that includes vascular disease. Cardiovascular research is the umbrella for everything from molecular studies of heart muscle to randomized trials of therapies, and it is carried out by cardiologists, but also by physiologists, geneticists, epidemiologists, biostatisticians and biomedical engineers. Cardiac surgery is a separate surgical specialty that works closely with cardiology. Research administrators will see all of these labels on proposals and should treat them as overlapping communities rather than strict categories.

Major Subfields of Cardiology

• General and preventive cardiology — risk assessment, blood pressure and lipid management, and long-term prevention of cardiovascular disease.
• Interventional cardiology — catheter-based diagnosis and treatment, including opening narrowed coronary arteries and repairing structural heart problems without open surgery.
• Electrophysiology — the heart’s electrical system, rhythm disorders, ablation procedures and implanted rhythm devices.
• Heart failure and transplant cardiology — management of weakened or stiff hearts, mechanical circulatory support and heart transplantation.
• Cardiac imaging — echocardiography, nuclear imaging, cardiac CT and cardiac MRI, covered in more detail below.
• Pediatric and adult congenital heart disease — structural heart conditions present from birth, followed from infancy into adulthood.
• Cardio-oncology — heart health in people receiving cancer treatment, an area that overlaps with oncology and pharmacology.
• Cardiovascular genetics and genomics — inherited cardiomyopathies, arrhythmia syndromes and lipid disorders, plus genome-wide studies of common heart disease (see What Is Genomics?).
• Vascular medicine and critical-care cardiology — diseases of arteries and veins outside the heart, and intensive management of the acutely ill cardiac patient.

How Cardiology Relates to Neighboring Disciplines

The heart does not work alone, and cardiovascular research borders many fields. Its closest neighbors on this site are pulmonology (the heart and lungs share a circulation and often share patients), nephrology (kidney disease and cardiovascular disease strongly influence each other), endocrinology (diabetes and lipid metabolism), neurology (stroke is a vascular disease of the brain), hematology (clotting and anticoagulation) and geriatrics. Methods come from epidemiology, biostatistics, pharmacology, radiology and biomedical engineering. For the wider map, see the overview of the branches of science.

Common Research Methods and Tools

• Population cohorts and registries — long-running observational studies that follow participants over many years to relate risk factors to later events. The Framingham Heart Study, which the National Heart, Lung, and Blood Institute (NHLBI) describes as launched in 1948 with 5,209 men and women aged 30 to 62 from Framingham, Massachusetts, is the best-known example; NHLBI credits it with identifying high blood pressure, high cholesterol and cigarette smoking as major cardiovascular risk factors. See longitudinal study design and cohort studies for the methodology.
• Randomized clinical trials — the standard for testing drugs, devices and strategies, discussed under endpoints below.
• Electrocardiography and monitoring — recording the heart’s electrical activity at rest, during exercise or continuously with wearable and implanted monitors.
• Cardiac imaging — echocardiography (ultrasound of the heart), nuclear perfusion imaging, cardiac CT, cardiac MRI and invasive coronary angiography. For the broader field, see What Is Medical Imaging?; for equipment budgeting, see the MRI machine cost guide.
• Cardiac catheterization — passing catheters through blood vessels to measure pressures, image vessels and deliver treatment.
• Genetics and omics — sequencing for inherited heart conditions and genome-wide association studies for common disease.
• Animal and cell models — rodent and large-animal models, engineered heart tissue and stem-cell-derived cardiomyocytes, conducted under the same oversight as other vertebrate work (see the animal research ethics guide and the technique-level note on cardiac puncture in mice).
• Computational modelling — simulation of blood flow and electrical propagation, and machine-learning analysis of ECGs and images, which raises its own regulatory questions (see software as a medical device).

Cardiac Devices and Their Regulation

Cardiology is unusually device-intensive. Implanted pacemakers and defibrillators, stents, prosthetic and transcatheter valves, ventricular assist devices, ablation catheters and wearable monitors all sit alongside drugs as core therapies, and many cardiology trials test devices rather than molecules. That matters for administrators: device studies follow different regulatory pathways than drug studies, including investigational-device rules (see the dictionary entry on the investigational device), and the first question on a device protocol is often how the product is classified. For orientation, see What Is a Medical Device?. Everyday clinical hardware is covered in guides such as What Is a Stethoscope? and What Is a Pulse Oximeter?, and the difference between emergency defibrillation tools is explained in manual defibrillator vs. AED. Clinic-level equipment lists are a separate topic, handled in the cardiology office supply checklist, which is a practical purchasing guide rather than a discipline overview.

Clinical Scores and Risk Tools

Cardiology research and practice lean heavily on standardized scoring systems, which also serve as inclusion criteria and stratification variables in trials. CASRAI has reference pages for several of them: the TIMI score for risk stratification in acute coronary syndromes, the Killip classification for heart failure severity after a heart attack, and the CHA2DS2-VASc score for stroke risk in atrial fibrillation. Reading a cardiology protocol is much easier once these names are familiar.

Trial Endpoints and MACE

Cardiovascular disease is common and its serious events (heart attack, stroke, death) are relatively infrequent in any single patient, so cardiology trials are often large and long, and endpoint selection is a central design decision. Typical cardiovascular trial outcomes include:

• Mortality — death from any cause or from cardiovascular causes, clinically unambiguous but requiring large samples.
• Clinical events — myocardial infarction (heart attack), stroke, hospitalization for heart failure, and repeat revascularization.
• Physiological and imaging measures — blood pressure, cholesterol levels, ejection fraction or other imaging parameters, used as surrogates or secondary outcomes.
• Patient-reported outcomes — symptoms, function and quality of life.

MACE, short for major adverse cardiovascular events, is a composite endpoint: a single outcome that counts a participant as having an event if any one of several component events occurs. Because the component list is chosen by each trial, MACE is not one universal definition. Components commonly include cardiovascular death, nonfatal myocardial infarction and nonfatal stroke, with some trials adding further events such as hospitalization for unstable angina or coronary revascularization, which is why people refer to “three-point” or “four-point” MACE. When reviewing a protocol, always read the exact component list rather than assuming. Composites increase the number of events and therefore statistical power, but they can mislead if the components differ greatly in clinical importance (see the dictionary entry on composite endpoints). Trials with event-based endpoints typically use an independent group to judge whether reported events meet the protocol definitions (see endpoint adjudication committees), and surrogate measures such as blood pressure or cholesterol need validation before they can stand in for clinical outcomes (see surrogate endpoint validation). For design background, see designing a clinical trial and non-inferiority vs. superiority trial design.

How Cardiovascular Research Is Funded

In the US, the lead federal funder of heart research is the National Heart, Lung, and Blood Institute (NHLBI), part of the National Institutes of Health. NHLBI describes its mission as providing global leadership for a research, training and education program to promote the prevention and treatment of heart, lung and blood disorders, and describes itself as one of the largest institutes and centers within NIH, located in Bethesda, Maryland. Its remit covers heart, lung, blood and sleep disorders, so cardiology investigators also commonly encounter other NIH institutes whose missions touch cardiovascular health, such as those focused on stroke or aging. Details of structure, priorities and budgets change, so confirm them on the funder’s site.

Funding mechanisms vary: investigator-initiated research grants, large consortia and networks that commonly use cooperative agreements such as the U01, and mentored career awards. Early-career investigators commonly enter through awards such as the K99/R00, and competitiveness varies by institute and year (see NIH paylines for FY2026). Data generated with NIH funding is subject to data-sharing policy (see the NIH Data Management and Sharing Plan guide).

Outside government, voluntary health organizations are a major funding source. The American Heart Association (AHA) is the best-known in the US cardiovascular field, and CASRAI covers one of its early-career programs in the AHA Career Development Award guide. Industry funds a large share of late-phase drug and device trials, so sponsor-investigator agreements and conflict-of-interest management are routine in cardiology departments. For the funder landscape beyond government, see the disease charity research funding guide. Funding opportunities and priorities change, so always confirm current details with the funder.

Societies, Guidelines and Journals

Two US bodies dominate the field’s public identity. The American College of Cardiology (ACC) describes its founding in 1949 by 13 cardiologists, led by Franz Groedel and Bruno Kisch, and states a mission to transform cardiovascular care and improve heart health for all. It publishes the Journal of the American College of Cardiology (JACC) along with a family of JACC-branded journals on topics such as imaging, heart failure and clinical electrophysiology. The American Heart Association (AHA) is a voluntary health organization that funds research and publishes scientific journals, and the two organizations have both issued clinical practice guidelines that trial protocols and hospital policies frequently cite. In Europe the European Society of Cardiology plays a comparable role. Guidelines are periodically revised, so cite the current version and its publication date rather than a remembered one.

A Brief History

Modern cardiology grew out of two developments: the ability to measure the heart (the electrocardiogram, cardiac catheterization and later echocardiography and other imaging) and the move from describing disease to measuring risk in populations. The Framingham Heart Study, launched in 1948 according to NHLBI, helped establish the idea of cardiovascular “risk factors,” and NHLBI reports that it has produced approximately 6,000 articles in leading medical journals. Professional organization followed: the ACC dates its founding to 1949. Later decades brought coronary care units, catheter-based interventions, implantable rhythm devices and large pragmatic trials, which together made cardiology one of the most trial-intensive specialties in medicine. This page deliberately limits itself to historical points that can be attributed to a named source; for detailed chronologies consult a dedicated medical history.

Career and Training Pathways

The clinical path runs through medical school, an internal medicine residency (or pediatrics, for pediatric cardiology) and a cardiovascular disease fellowship, followed in many cases by additional subspecialty training in areas such as interventional cardiology, electrophysiology, advanced heart failure or imaging. In the US, board certification is administered through the American Board of Internal Medicine; because training lengths and examination requirements are revised from time to time, confirm the current requirements directly with the board and with ACGME-accredited programs. Physician-scientists often add research years and a mentored career award. Non-clinician researchers enter through PhD programs in physiology, bioengineering, epidemiology or genetics. Support staff include cardiac sonographers, cardiovascular technologists, catheterization-lab nurses and clinical research coordinators, and research offices should plan for these roles when budgeting.

Why Cardiology Matters for Research Administration

Cardiology generates a distinctive administrative workload. Studies are frequently large, multi-site and long, which drives complicated subaward and budget structures (see the cost of running a clinical trial). Device trials add regulatory submissions and implant tracking; imaging and core-lab work adds image transfer, storage and data-use agreements; event adjudication adds committee charters and blinded data flows; and long follow-up requires retention plans and data and safety monitoring. Funders increasingly expect shared data, and trial oversight practice is evolving (see risk-based quality management in clinical trials). Knowing the field’s vocabulary helps administrators ask the right questions of principal investigators early.

Frequently Asked Questions

What is cardiology in simple terms?

Cardiology is the branch of medicine that deals with the heart and blood vessels, including the diagnosis, treatment and prevention of conditions such as coronary artery disease, heart failure and abnormal heart rhythms, together with the research that supports that care.

What does a cardiologist do?

A cardiologist is a physician who evaluates and manages heart and circulatory conditions, using history, examination, electrocardiograms, imaging, stress testing, medications and, for those with procedural training, catheter-based or device-based treatments. Cardiologists who perform surgery on the heart are cardiac surgeons, a separate specialty. This is general information, not medical advice.

What is the difference between cardiology and cardiovascular research?

Cardiology is the medical specialty. Cardiovascular research is the broader scientific effort, which includes cardiologists but also basic scientists, epidemiologists, statisticians and engineers, and ranges from laboratory studies to population cohorts and clinical trials.

What does MACE mean in a clinical trial?

MACE stands for major adverse cardiovascular events. It is a composite endpoint whose exact components are defined by each trial; common components are cardiovascular death, nonfatal heart attack and nonfatal stroke, sometimes with additional events. Always check the protocol definition.

Who funds heart research?

In the US, the main public funder is NHLBI within NIH, supplemented by other institutes, voluntary organizations such as the American Heart Association, and industry sponsors of drug and device trials.

What is the difference between ACC and AHA?

Both are US nonprofit organizations active in cardiovascular science. The American College of Cardiology is a professional society of cardiovascular clinicians and researchers that publishes JACC; the American Heart Association is a voluntary health organization that funds research and public education.

Is there a guide to equipping a cardiology clinic?

Yes, but it is a different topic from this page: see the cardiology office supply checklist.